Ion source device having control means for reducing filament current below its starting value

ABSTRACT

An ion source device of the Duoplasmatron type has a current reduction resistor in the filament circuit thereof for reducing the filament current during steady state operation thereof, and a relay adapted to normally short-circuit both terminals of the current reduction resistor, which relay is energized by a current flowing through an intermediate electrode circuit so as to open both of these terminals of the resistor thereby making it possible to reduce the steady state filament current.

United States Patent Kondo et a1.

[54] ION SOURCE DEVICE HAVING CONTROL MEANS FOR REDUCING FILAMENTCURRENT BELOW ITS STARTING VALUE Inventors: Toshio Kondo/Kokubunji;Hifumi 'Iamura, Hachioji, both of Japan Assignee: Hitachi, Ltd., Tokyo,Japan Filed: 1811.11, 1971 Appl. No.: 105,321

' Foreign Application Priority Data Jan. 9, 1970 Japan "45/5124 US. Cl..315/74, 315/107, 3l5/DlG. 5 Int. Cl ..H0lj 33/00 Field of Search.....315/107, 106, 74, DIG. 5;

[56] References Cited UNITED STATES PATENTS 2 ,5 1 9 1 gt 31:11:23.1:11:. Y

[ 1 Oct. 17, 1972 3,413,517 11/1968 Barber et a1. ..3l5/l07 X 3,567,9953/1971 Lauritzen et a1. ...3 15/106 UX Primary Examiner-Paul L. GenslerAttorney-Craig, Antonelli, Stewart & Hill [57] ABSTRACT 6 Claims, 2Drawing Figures '5 up l2 '3 DC. HEATING i I m I I l4 l4 DC. ACCELER- IATING VOLT- 1 AGE SOURCE l6 i L L WEI. 3 2 4 9 I7 18 ,7 Y \s 1 & IONACCELER---- ATING H VOLI- g 5 IAGE SOURCE 1 PATE'NTEDocmmz g I 3,699,381

05:. HEATING L,

ANODE CURRENT (A) 'l 2 3 4 5 6 FILAMENT CURRENT (A) INVENTORS TosmoKONDO AND HIFUMH rmu'm Gnu l9, qnlbnalligsicuxml I I AT TORNEYS IONSOURCE'DEVICEHAVING CONTROL MEANS FOR REDUCING FILAMENT CURRENT BELOW ls STARTING VALUE This inventionrelates to an ion source device for anion microanalyzer and the like and, more particularly, to an ion sourcedevice of the Duoplasmatron type having means for reducing the filamentcurrent during steady state operation thereof.

BACKGROUND OF THE INVENTION filament current is less than that of thestarting filament current. Therefore, it is apparent that in suchconventional devices the steady state filamentv current has anunnecessarily large value and thus the life of the filament thereinbecomes very short.

SUMMARY OF TI-IE'INVENTION An object of this invention is to providemeans for making it possible to reduce the steady filamentcurrent in anion microanalyzer of the type described.

This invention is characterized in that a current reduction resistor isinserted in the filament heating circuit and switching means is arrangedso as to short-circuit both terminals of the reduction resistor. With aview to function, when said discharge occurs, the switching means isenergized by a current flowing through an intermediate electrode circuitwhich causes both terminals to open so that the filament current flowsthrough the current reduction resistor and the steady state filamentcurrent for maintaining discharge is reduced.

This and other objects, advantages andfeatures of the present inventionwill become more apparent from the following detailed description withreference to the accompanying drawings, wherein:

FIG. I is a schematic circuit diagram indicating an I embodiment of thisinvention.

FIG. 2 shows the relationship between filament current and anode currentin an ion source device.

DESCRIPTION OF A PREFERRED EMBODIMENT In FIG. I, a filament 2 isconnected to a d. c. heating power source 1 which provides heatercurrent thereto, and a d. c. accelerating voltage source 3 is connectedbetween an intermediate electrode 4 and the filament 2 so as toaccelerate electrons emitted from said filament.

A magnet 6 made Of ferrite is disposed between said intermediateelectrode 4 and an anode 5 so as to insulate these elements and toconcentrate the electrons in the space therebetween. A gas having aconstant quantity is supplied to a space adjacent to said intermediateelectrode 4 by proper means (not shown) and ionized as a result ofdischarge occurring due to impingement v with said electrons.

An ion accelerating high voltage source 7 is connected between saidanode 5 and an extractor 8 so that the ions are extracted therefrom bysaid extractor 8 and further are introduced into an ion microanalyzer(not shown) so that the ions are directed to a speciment in a knownmanner. Moreover, aresistor 9 is inserted in said intermediate electrodecircuit. Both secondary windings of the insulating transformers l0 and11 are connected to the respective inputs of the power sources 1 and 3,and both primary windings thereof are connected to an a. 0. power source(not shown).

In the ion source device as above-described, there is a relationshipbetween the filament current and the anode current as shown in FIG. 2.As is apparent from said'relationship, even if the minimum steadyfilament current I is less than the starting filament current Idischarge caused to occur once can be maintained.

According to this invention, in order to attain a reduction in thesteady filament current, a current reduction resistor 13 and a relay 16having an exciting coil 17 and a contact 18- are disposed in the system,in addition to the above-described elements. The current reductionresistor 13 is inserted in the filament circuit 12, the exciting coil 17is inserted in an intermediate electrode circuit 15 and the contact 18is selectively connected between the terminals 14 and 14 of thereduction resistor 13 to provide an open or short-circuit therebetween.Further, relay 16 is adapted to normally short-circuit both terminals 14and 14' of the reduction resistor 13 when a current does not flowthrough the circuit 15, namely, the contact 18 is a socalled breakcontact which remains closed when the relay 16 is not energized.

Now, when the filament current whose value is larger than that of saidstarting filament current is applied to said filament 2, a dischargebegins. As a result of said discharge, the current flows through thecircuit 15 and energizes the relay 16, so that the contact 18 opens andthe filament current flows through the reduction resistor 13.Consequently, the value of the filament current becomes less than thatof the starting filament current. The contact 19 is kept in the openstate during further operation of the ion source device.

According to this invention, since it is possible to reduce the filamentcurrent during steady state operation of said ion source device, thelife of the filament can be extended remarkably as compared with theprior art.

While we have shown and described one embodiment in accordance with thepresent invention, it is understood that the same is not limited theretobut is susceptible of numerous changes and modifications as known to aperson skilled in the art, and we therefore do not wish to be limited tothe details shown and described herein but intend to cover all suchchanges and modifications as are obvious to one of ordinary skill in theart.

We claim:

1. In an ion source device for an ion micro-analyzer and the likecomprising a filament for emitting electrons,

an intermediate electrode for accelerating said electrons emitted fromsaid filament,

a heating power source connected in circuit to said filament forsupplying a filament current to said filament at a starting valuenecessary to initiate a gaseous discharge in the space adjacent saidintermediate electrode,

a first voltage source connected between said filament and saidintermediate electrode,

anode means for accelerating ions produced in the space adjacent saidintermediate electrode,

a magnet disposed between said intermediate electrode and said anode forconcentrating said ions, and

an extractor of said ions and a second voltage source connected betweensaid extractor and said anode,

the improvement which comprises filament current control meansresponsive to a discharge current flowing from said first voltage sourceto said intermediate electrode for reducing and maintaining saidfilament current at a lesser value than said starting value, whichlesser value is still sufficient to maintain said discharge.

2. The combination defined in claim 1, wherein said filament currentcontrol means includes switching means for selectively increasing theresistance of said filament circuit in response to detection of saiddischarge current.

3. The combination defined in claim 1, wherein said magnet is made of anelectrical insulating material and is disposed in contact with saidintermediate electrode and said anode.

4. The combination defined in claim 1, wherein said filament currentcontrol means includes a current reduction resistor connected in seriesbetween said filament and said heating power source, and switching meansnormally short-circuiting said current reduction resistor for removingsaid short-circuit in response to said discharge current, so as toreduce said filament current in the steady operating state of saiddevice.-

5. The combination defined in claim 4, wherein said switching meansincludes a movable switch contact normally connected across said currentreduction resistor and an operating winding connected between said firstvoltage source and said intermediate electrode for actuating saidmovable switch contact when energized by current flow.

6. The combination defined in claim 5, wherein said magnet is made of anelectrical insulating material and is disposed in contact with saidintermediate electrode and said anode.

1. In an ion source device for an ion micro-analyzer and the likecomprising a filament for emitting electrons, an intermediate electrodefor accelerating said electrons emitted from said filament, a heatingpower source connected in circuit to said filament for supplying afilament current to said filament at a starting value necessary toinitiate a gaseous discharge in the space adjacent said intermediateelectrode, a first voltage source connected between said filament andsaid intermediate electrode, anode means for accelerating ions producedin the space adjacent said intermediate electrode, a magnet disposedbetween said intermediate electrode and said anode for concentratingsaid ions, and an extractor of said ions and a second voltage sourceconnected between said extractor and said anode, the improvement whichcomprises filament current control means responsive to a dischargecurrent flowing from said first voltage sOurce to said intermediateelectrode for reducing and maintaining said filament current at a lesservalue than said starting value, which lesser value is still sufficientto maintain said discharge.
 2. The combination defined in claim 1,wherein said filament current control means includes switching means forselectively increasing the resistance of said filament circuit inresponse to detection of said discharge current.
 3. The combinationdefined in claim 1, wherein said magnet is made of an electricalinsulating material and is disposed in contact with said intermediateelectrode and said anode.
 4. The combination defined in claim 1, whereinsaid filament current control means includes a current reductionresistor connected in series between said filament and said heatingpower source, and switching means normally short-circuiting said currentreduction resistor for removing said short-circuit in response to saiddischarge current, so as to reduce said filament current in the steadyoperating state of said device.
 5. The combination defined in claim 4,wherein said switching means includes a movable switch contact normallyconnected across said current reduction resistor and an operatingwinding connected between said first voltage source and saidintermediate electrode for actuating said movable switch contact whenenergized by current flow.
 6. The combination defined in claim 5,wherein said magnet is made of an electrical insulating material and isdisposed in contact with said intermediate electrode and said anode.